Tetrahydropyrimidine-isocyanate addition products

ABSTRACT

New amidine/isocyanate adducts are particularly useful as catalysts for hardening epoxy resins, in particular pulverulent coating compositions based on epoxy resins. New bicyclic amidines are excellent starting materials for manufacturing these amidine/isocyanate adducts.

This application is a division of application Ser. No. 317,299 filedNov. 2, 1981, now U.S. Pat. No. 4,424,353.

This invention relates to new bicyclic amidines and newamidine/isocyanate adducts and to processes for the preparation thereofand to the use thereof as catalysts for hardening epoxide resins, i.e.thermosetting compounds based on polyepoxides and optionally polymerscontaining carboxylic groups. The properties of the amidine/isocyanateadducts according to the present invention are particularly useful whenthese substances are used as hardeners for powder lacquer binders.

Pulverulent coatings which may be applied to a substrate by whirlsintering, flame spraying or the electrostatic powder spray process areknown. They should be capable of being converted into cross-linkedcoatings by a stoving treatment carried out at moderately hightemperatures for as short a time as possible. It should be borne in mindthat, while there is a demand for ever shorter stoving times at lowertemperatures, which means higher reactivity, no reaction should takeplace between the resin and hardener when the mixture of binder,pigments, fillers and optionally other auxiliary agents is extruded attemperatures of from 80° to 160° C., preferably from 90° to 120° C.

Although it is possible to equip the resin component with such a largenumber of carboxyl groups that complete reaction is achieved understoving conditions of from 150° to 160° C./30 minutes, the high acidnumber causes an unwanted preliminary reaction to take place even duringthe extrusion process and this reaction may only be kept withintolerable limits by vigorous cooling of the extrudate. The storagestability is also impaired since an unwanted reaction takes place evenat room temperature and adversely affects the levelling of the powderlacquer and/or the mechanical properties of the stoved lacquer coat.

A powder lacquer binder consisting of a carboxyl group-containingpolyester and triglycidyl isocyanurate has been disclosed in GermanOffenlegungsschrift No. 2,163,962 (see Claim 4). Binders of this typeare said to produce weather-resistant (chalking-resistant) lacquercoats. The stoving conditions of such systems are normally 200° C./10minutes or 160° C./30 minutes for layer thicknesses of from 40 to 120μm. There has therefore been a demand for powder lacquers which may behardened under more favourable conditions without any loss in levellingproperties or storage stability.

It has now surprisingly been found that catalysts based on certainisocyanate-masked amidines are capable of withstanding unharmed theextrusion of the starting components to powder lacquers ready for useand do not become active until the final heat hardening process.

Guanidines are to be regarded as a sub-class of amidines for thepurposes of the present invention and will therefore also be referred toas "amidines".

The present invention relates to bicyclic amidines corresponding to thefollowing general formula: ##STR1## wherein R¹ represents a hydrogenatom or an alkyl group having from 1 to 4 carbon atoms, preferably ahydrogen atom or a methyl group; and

R² represents a hydrogen atom, an alkyl group having from 1 to 18 carbonatoms, a cycloalkyl group having from 5 to 14 carbon atoms, an aralkylgroup having from 7 to 16 carbon atoms or an aryl group having from 6 to20 carbon atoms.

The following compounds are preferred amidines (I): ##STR2##

The above formulae indicated by odd Roman numerals are abbreviated formsof representing the four different isomers in which the methyl group isin the 4-, 5-, 6- and 7-position, respectively. 4- and 7-methylderivatives are preferred.

The amidines (I) may be prepared by known methods, preferably byreaction of cycloaliphatic diamines (XVIII) with monocarboxylic acids(XIX) which are preferably saturated or with the reactive derivativesthereof (XIX): ##STR3## wherein R¹ and R² are as defined above;

R³ represents COCl, CN, or CO₂ R⁴ ; and

R⁴ represents a hydrogen atom, C₁ -C₆ alkyl, phenyl or benzyl.

Apart from 1,3-diaminocyclohexane itself, preferred compounds (XVIII)include in particular the methyl-1,3-diaminocyclohexanes formed byhydrogenation of tolylene diamines which are obtainable on a largetechnical scale. The 2,4- and 2,6-diaminoisomers and mixtures thereofare equally suitable.

Preferred carboxylic acids (XIX) include formic acid, acetic acid,propionic acid, butyric acid, 2-ethyl hexanoic acid, stearic acid,benzoic acid and phenyl acetic acid.

The present invention also relates to a process for the preparation ofamidines (I) from the compounds (XVIII) and (XIX), characterised in thatcompounds (XVIII) and (XIX) are reacted in proportions corresponding tofrom 2.5 mol, preferably from 1 to 1.5 mol, of diamine (XVIII) per molof carboxylic acid (derivative) group of compound (XIX) at from 150° to280° C., preferably from 200° to 250° C., for from 2 to 10 hours.

The excess of diamine (XVIII) has been found to be advantageous since itis less favourable to the formation of the corresponding diamide. It isadvisable to use a catalyst in some cases.

Although bicyclic amidines (I) are known from German OffenlegungsschriftNo. 2,722,514 (formula Ic on page 8), the formula in question covers5-membered rings, as well as 6- and 7-membered rings, and since thesecompounds known from the literature are accelerators for the preparationof polyureas, the literature gives no indication that the amidines (I)according to the present invention may be used in an isocyanate-maskedform as catalysts for the hardening of epoxide resins.

Amidines of the imidazole-type and the use thereof for bondingthermosetting one-component epoxide systems have been disclosed inGerman Offenlegungsschrift No. 2,731,335, but these imidazolines are inmost cases insufficiently reactive for hardening powder lacquers basedon epoxide resins.

Amidines of the tetrahydropyrimidine-type and the use thereof forblocking polyisocyanates have been described in GermanOffenlegungsschrift No. 2,751,805. The blocked polyisocyanates are saidto be suitable as catalysts for the anionic polymerisation ofε-caprolactam and the preparation of wire lacquers. Amidines (I)according to the present invention are neither described nor in any waysuggested in German Offenlegungsschrift No. 2,751,805.

The present invention also relates to addition products obtainable frompolyisocyanates, preferably from polyisocyanates having from 4 to 25, inparticular from 4 to 16, carbon atoms and from 2 to 4, preferably 2,isocyanate groups, and amidines (I).

Preferred polyisocyanates for the reaction with amidines (I) to formisocyanate addition products include aliphatic, cycloaliphatic,araliphatic, i.e. aryl-substituted aliphatic, and/or aromaticdiisocyanates, such as those described in "Methoden der organischenChemie" (Houben-Weyl), Vol. 14/2, 4th Edition; Georg Thieme-Verlag,Stuttgart 1963, pages 61-70, and by W. Siefken, Liebigs Ann. Chem. 562,75-136, e.g. the following: 1,2-ethylene diisocyanate,1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-and 2,4,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecanediisocyanate, 107,ω-diisocyanatodipropyl ether,cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and 1,4-diisocyanate,2,2- and 2,6-diisocyanato-1-methyl cyclohexane,3-isocyanatomethyl-3,5,5-trimethyl cyclohexyl isocyanate ("isophoronediisocyanate"), 2,5- and3,5-bis-(isocyanatomethyl)-1,4-methano-decahydronaphthalene, 1,5-, 2,5-1,6- and 2,6-bis-(isocyanato-methyl)-4,7-methano-hexahydroindane, 1,5-,2,5-, 1,6- and 2,6-bis-(isocyanato)-4,7-methano-hexahydroindane,dicyclohexyl-2,4'- and 4,4'-diisocyanate, 2,4- and2,6-hexahydrotolylenediisocyanate, perhydro-2,4'- and4,4'-diphenylmethanediisocyanate, ω,ω'-diisocyanato-1,4-diethylbenzene,1,3- and 1,4- phenylene diisocyanate, 4,4'-diisocyanatodiphenyl,4,4'-diisocyanato-3,3'-dichlorodiphenyl,4,4'-diisocyanato-3,3'-dimethoxy-diphenyl,4,4'-diisocyanato-3,3'-dimethyl-diphenyl,4,4'-diisocyanato-3,3'-diphenyldiphenyl, 2,4'- and4,4'-diisocyanato-diphenylmethane, naphthylene-1,5-diisocyanate,mixtures of tolylene diisocyanates, 2,4- and 2,6-tolylene diisocyanate,N,N'-(4,4'-dimethyl-3,3'-diisocyanatodiphenyl)-uretdione andm-xylylene-diisocyanate, but also triisocyanates, such as2,4,4'-triisocyanatodiphenyl ether, 4,4'-4"-triisocyanato-triphenylmethane and tris-(4-isocyanatophenyl)-thiophosphate, and mixtures ofthese isomers may also be used.

As a general rule, it is particularly preferred to use commerciallyreadily available aliphatic, cycloaliphatic or aromatic diisocyanates,in particular hexamethylene diisocyanate,3-isocyanatomethyl-3,5,5-trimethyl-cyclohexylisocyanate and 2,4- and2,6-tolylene diisocyanate and isomeric mixtures thereof.

Other preferred polyisocyanates for the preparation of theamidine/polyisocyanate addition products are the prepolymers obtainablefrom the above-mentioned polyisocyanates and polyhydric alcohols havingfrom 2 to 12 carbon atoms and from 2 to 6 OH groups. Other preferredpolyisocyanates are formed by auto-addition of some of theabove-mentioned polyisocyanates. They may contain biuret, uretdione,uretone imine, isocyanurate, urea and/or allophanate groups in additionto the free isocyanate groups.

The present invention further relates to a process for the preparationof the above-mentioned addition products, characterised in that theamidines (I) and polyisocyanates are reacted at from 50° to 150° C.,preferably from 80° to 120° C., in proportions providing from 0.8 to 3,preferably from 0.95 to 1.5, isocyanate groups per NH group of theamidines (I).

It goes without saying that whichever of the components is more easilydosed at the reaction temperature employed should be added to the heatedreactant in the reaction vessel. Liquid polyisocyanates are thereforepreferably added to the liquid amidine (I).

The reaction may be carried out with or without inert solvents.Preferred solvents include ketones, such as acetone, methyl ethylketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone;aromatic solvents, such as benzene, toluene, xylenes, chlorobenzene andnitrobenzene; cyclic ethers, such as tetrahydrofuran and dioxane;esters, such as methyl acetate and n-butyl acetate; aliphaticchloro-hydrocarbons, such as chloroform and carbon tetrachloride; andaprotic solvents, such as dimethyl formamide, dimethyl acetamide anddimethyl sulphoxide.

After termination of the reaction, the solvent may be removed and theresulting amidine/polyisocyanate addition products according to thepresent invention are discharged and converted into a form suitable forfurther use.

The amidine/polyisocyanate adducts according to the present inventiongenerally have a particular molecular weight resulting from the natureand quantity of the starting components. If a polyisocyanate mixturecontaining molecules having differing molecular weights is used, theaddition products obtained have a particular molecular weightdistribution. They have in most cases an average molecular weight M_(n)of from 200 to 3000, preferably from 300 to 1000, (determined by vapourpressure osmometry in acetone) and melt in the region of from 30° to220° C., preferably from 80° to 160° C. (DIN 53 180).

The present invention also relates to addition products obtainable frommonoisocyanates having from 2 to 20 carbon atoms and amidines whichcontain at least once the structure: ##STR4##

Preferred monoisocyanates include alkyl, cycloalkyl, aralkyl and arylisocyanate having from 2 to 20 carbon atoms, e.g. the following:

methyl isocyanate,

ethyl isocyanate,

propyl isocyanate,

butyl isocyanate,

2-ethyl-hexyl isocyanate,

6-chlorohexyl isocyanate,

stearyl isocyanate,

phenyl isocyanate, and

benzyl isocyanate.

The less volatile isocyanates having at least 6 carbon atoms arepreferably used, in particular 6-chlorohexyl isocyanate and stearylisocyanate.

Among the above-mentioned amidines (XX) and (XXI), amidines (I) areparticularly preferred. Other preferred amidines (XX) and (XXI) are theimidazolines corresponding to the following general formula: ##STR5##wherein R⁵, R⁶, R⁷ and R⁸ independently represent a hydrogen atom, analkyl group having from 1 to 6 carbon atoms, a cycloalkyl group havingfrom 5 to 10 carbon atoms, an aralkyl group having from 7 to 12 carbonatoms, an aryl group having from 6 to 15 carbon atoms or a heterocyclicgroup having from 5 to 10 carbon atoms and 1 or 2 oxygen and/or nitrogenand/or sulphur atoms; and

R⁹ represents an alkyl or alkylene group having from 1 to 6 carbonatoms, an aryl or arylene group having from 6 to 15 carbon atoms, eachof which may be substituted by alkyl, cycloalkyl, aralkyl, aryl orheterocyclic groups (as defined for R⁵, R⁶, R⁷ and R⁸);

n represents 1 or 2; and

R⁹ may also represent a hydrogen atom when n represents 1.

The following are examples of preferred imidazolines (XXII):2-phenyl-imidazoline, 2-phenyl-4-methyl-imidazoline,2-(m-tolyl)-4-methyl-imidazoline, 2-(m-pyridyl)-imidazoline,1,4-tetramethylene-bis-(4-methyl-imidazoline-2), 2-methyl-imidazoline,2,4-dimethyl-imidazoline, 2-ethyl-imidazoline,2-ethyl-4-methyl-imidazoline, 2-benzyl-imidazoline,2-(o-tolyl)-imidazoline, 2-(p-tolyl)-imidazoline,tetramethylene-bis-imidazoline,1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline,1,1,3-trimethyl-1,4-tetramethylene-bis-4-methyl-imidazoline,1,3,3-trimethyl-1,4-tetramethylene-bis-4-methyl-imidazoline,1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-4-methyl-imidazoline.Mixtures of the imidazoline derivatives may also be used.2-phenyl-imidazoline and 2-methyl-imidazoline are particularlypreferred.

Preferred amidines (XX) and (XXI) also include tetrahydropyrimidinescorresponding to the following general formula: ##STR6## wherein R¹⁰ toR¹⁶ independently represent a hydrogen atom, an alkyl group having from1 to 6 carbon atoms, a cycloalkyl group having from 5 to 10 carbonatoms, an aralkyl group having from 7 to 12 carbon atoms or an arylgroup having from 6 to 15 carbon atoms,

and two geminal or vicinal substituents, together with the carbon atomto which they are attached, may also complete a cycloaliphatic ringhaving 5 or 6 carbon atoms.

The following are examples of preferred tetrahydropyrimidines (XXIII):2-methyl-tetrahydropyrimidine, 2,4-, 2,5- and2,6-dimethyl-tetrahydropyrimidine, 2-ethyl-tetrahydropyrimidine,2-ethyl-4-methyl-tetrahydropyrimidine, 2-benzyl-tetrahydropyrimidine,2-phenyl-tetrahydropyrimidine, 2-phenyl-4-methyl, -5-methyl- and-6-methyl-tetrahydropyrimidine, 2,4-diaza-3-phenyl-7,9,9- and7,7,9-trimethyl-bicyclo-(4,3,0)-nonene-2, and 2,4-diaza-3-methyl-7,9,9-and 7,7,9-trimethyl-bicyclo(4,3,0)-nonene-2 and mixtures thereof.

Preferred amidines (XX) and (XXI) also include compounds correspondingto the following general formula: ##STR7## wherein R¹⁷, R¹⁸ and R¹⁹ havethe same definition as R⁵ to R⁸, but

R¹⁷ and R¹⁸ are not members of a common ring.

The following are examples of preferred amidines (XXIV): formamidine,acetamidine, caproylamidine, benzamidine, benzyliminocaprolactam,n-butyl and t-butyliminocaprolactam, N-ethyl-N'-benzyl-benzamidine,N-t-butyl-N'-benzyl-acetamidine and N-n-butylamino-N'-benzylacetamidine.

The preferred amidines (XX) and (XXI) also include guanidinescorresponding to the following general formula: ##STR8## R²⁰, R²¹, R²²and R²³ independently represent a hydrogen atom, a C₁ -C₁₂ alkyl group,a C₅ -C₁₂ cycloalkyl group, a C₇ -C₁₂ aralkyl group, a C₆ -C₁₂ arylgroup or a C₁ -C₁₂ acyl group, preferably a C₁ -C₄ alkyl group or phenylgroup.

The following are examples of preferred guanidines (XXV):

N-methyl-guanidine,

N-ethyl-guanidine,

N-butyl-guanidine,

N-methyl-N'-ethyl-guanidine,

N,N'-dimethyl-guanidine,

N,N'-diethyl-guanidine,

N-methyl-N'-isopropyl-guanidine,

N,N'-dibutyl-guanidine,

N,N,N'-trimethyl-guanidine,

N,N,N',N'-tetramethyl-guanidine,

N,N,N',N'-tetraethyl-guanidine,

N-phenyl-guanidine,

N,N'diphenyl-guanidine,

N,N'-ditolyl-guanidine,

N-formyl-guanidine and

N-butyryl-guanidine.

The present invention also relates to a process for the preparation ofthe above-mentioned amidine/monoisocyanate addition products,characterised in that the amidines (XX) or (XXI) and themono-isocyanates having from 2 to 20 carbon atoms are reacted at from50° to 130° C., preferably from 80° to 110° C., in proportions providingfrom 0.8 to 1.1, preferably ca. 1, isocyanate group per NH group of theamidines (XX) or (XXI).

As regards the use of a solvent, the same rules apply as for theamidine/polyisocyanate addition products.

The present invention further relates to the use of theamidine/polyisocyanate and amidine/monoisocyanate addition productsaccording to the present invention as catalysts for hardeningthermosetting epoxide resins, in particular for hardening pulverulentcoating compounds based on polyepoxides and optionally polymerscontaining carboxyl groups.

The catalysts according to the present invention are generally used inquantities of from 0.1 to 5%, by weight, preferably from 1 to 2%, byweight, based on the sum of epoxide resin and any acid polymer present(exception see page 26). Addition of the catalyst is preferably carriedout at the stage of preparation of the finished powder lacquer system byextrusion.

The polyepoxides which may be used are solid, in most cases resinoussubstances which melt in the range of from 30° to 140° C., preferablyfrom 40° to 80° C., (determined by the method of differentialthermoanalysis), and contain, on average, more than one 1,2-epoxy groupper molecule.

The polyepoxide compounds may be based on polyhydric phenols, such aspyrocatechol, resorcinol, hydroquinone, 4,4'-dihydroxy-diphenyl methane,4,4'-dihydroxy-3,3'-dimethyl-diphenyl methane,4,4'-dihydroxy-diphenyldimethyl methane (bisphenol A),4,4'-dihydroxy-diphenylmethyl methane,4,4'-dihydroxy-diphenyl-cyclohexane,4,4'-dihydroxy-3,3'-dimethyl-diphenyl propane, 4,4'-dihydroxydiphenyl,4,4'-dihydroxy-diphenyl sulphone, tris-(4-hydroxy-phenyl)-methane,chlorination and bromination products of the above-mentioned diphenols,in particular of bisphenol A; novolaks (i.e. reaction products ofmonohydric or polyhydric phenols with aldehydes, in particularformaldehyde, in the presence of acid catalysts), diphenols obtained byesterification of 2 mols of the sodium salt of an aromatichydroxy-carboxylic acid with 1 mol of a dihalo alkane or dihalo dialkylether (see British Pat. No. 1,017,613), and polyphenols obtained by thecondensation of phenols with long-chain halogenated paraffins containingat least two halogen atoms (see British Pat. No. 1,024,288).

It is preferred to use commercially available solid epoxide resins ofthe type of diglycidyl ethers of bisphenol A (i.e. reaction products ofbisphenol A and epichlorohydrin) having an epoxide equivalent of from400 to 2500.

Compounds, such as (poly)glycidyl esters corresponding to the followinggeneral formula: ##STR9## wherein R²⁴ represents a straight- orbranched-chain saturated or unsaturated hydrocarbon group having from 4to 20 carbon atoms or a substituted or unsubstituted phenyl group, mayalso be used.

Compounds which may be used according to the present invention alsoinclude triglycidyl isocyanurate and/or its oligomers and triglycidylurazole and its oligomers, and mixtures thereof.

The polymers containing carboxyl groups may be polyester polycarboxylicacids prepared from polyols and polycarboxylic acids or derivativesthereof.

The polymers containing carboxyl groups should have a melting andsoftening range (determined by differential thermoanalysis) of from 20°to 150° C., preferably from 50° to 100° C., and an acid number of from10 to 150, preferably from 20 to 120, in particular from 30 to 50. TheOH numbers should preferably be below 20, in particular below 10.

The esterification reaction to synthesise the polyester carboxylic acidsmay be carried out by known methods of esterification of thecorresponding polycarboxylic acids and polyols, in particular ofdicarboxylic acids and dihydric alcohols, or by ester formation fromsuitable derivatives of these alcohols and carboxylic acids, such as theanhydrides, acid chlorides or hydroxy carboxylic acids.

Particularly preferred polyester polycarboxylic acids, i.e. those whichare at least trifunctional, are obtained by the incorporation ofpolycarboxylic acids or anhydrides thereof which are at leasttrifunctional, such as benzene-1,3,5-tricarboxylic acid or trimelliticacid anhydride.

Branched-chain polyester polycarboxylic acids may also be used. Thesemay be obtained by the incorporation of preferably aliphatic polyolscontaining at least three hydroxyl groups, such as trimethylol propaneor glycerol.

Suitable polycarboxylic acids for the preparation of the polyesterpolycarboxylic acids to be used according to the present inventioninclude in particular those corresponding to the following generalformula:

    A--COOH).sub.x                                             (XXVII)

wherein A represents a bond or an x-valent, substituted or unsubstitutedaliphatic group preferably having from 1 to 20 carbon atoms, acycloaliphatic group preferably having from 5 to 16 carbon atoms, analiphatic-aromatic group preferably having from 7 to 20 carbon atoms, anaromatic group preferably having from 6 to 15 carbon atoms or anaromatic or cycloalphatic group having from 2 to 12 carbon atoms andcontaining hetero-atoms, such as N, O or S in the ring; and x representsan integer of from 2 to 4, preferably 2 or 3.

The following are preferred examples of such polycarboxylic acids:oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid,trimethyladipic acid, azelaic acid, sebacic acid, decane dicarboxylicacid, dodecane dicarboxylic acid, fumaric acid, maleic acid,hexahydroterephthalic acid, phthalic acid, isophthalic acid,terephthalic acid, benzene-1,3,5-tricarboxylic acid,benzene-1,2,4-tricarboxylic acid, benzene-1,2,3-tricarboxylic acid,naphthalene-1,5-dicarboxylic acid, benzophenone-4,4'-dicarboxylic acid,diphenyl-sulphone-4,4'-dicarboxylic acid, butane-tetracarboxylic acid,tricarballylic acid, ethylene tetracarboxylic acid, pyromellitic acid,benzene-1,2,3,4-tetracarboxylic acid, benzene-1,2,3,5-tetracarboxylicacid and the acids corresponding to the following general formulae:##STR10## wherein X represents ##STR11##

The hydroxycarboxylic acids are preferably those corresponding to thefollowing general formula:

    (HOOC--).sub.y A(--OH).sub.z (XXVIII)

wherein A is as defined above; and y and z may represent, independentlyof each other, an integer of from 1 to 3, preferably 1 or 2.

Preferred examples are: glycollic acid, lactic acid, mandelic acid,malic acid, citric acid, tartaric acid, 2-, 3- and 4-hydroxybenzoic acidand hydroxybenzene-dicarboxylic acids.

The polyols required for the preparation of the polyester polycarboxylicacids include in particular those corresponding to the following generalformula:

    B(--OH).sub.a                                              XXIX

wherein B represents an a-valent aliphatic group having from 2 to 20carbon atoms, a cycloaliphatic group having from 5 to 16 carbon atoms,an araliphatic group having from 7 to 20 carbon atoms, an aromaticgroup, having from 6 to 15 carbon atoms or a heterocyclic group havingfrom 2 to 12 carbon atoms containing N, O or S; and a represents aninteger of from 2 to 6, preferably 2 or 3.

The following are preferred examples of such polyols: ethylene glycol,1,2- and 1,3-propane diol, 1,2, 1,3-, 1,4- and 2,3-butane diol,1,5-pentane diol, 2,2-dimethyl-1,3-propane diol, 1,6- and 2,5-hexanediol, 1,12-dodecane diol, 1,12-octanedecane diol, 2,2,4- and2,4,4-trimethyl-1,6-hexane diol, trimethylol propane, trimethylolethane, glycerol, 1,2,6-hexane triol, pentaerythritol, mannitol,1,4-bis-hydroxymethylcyclohexane, cyclohexane-1,4-diol,2,2-bis-(4-hydroxycyclohexyl)-propane, bis(4-hydroxyphenyl)-methane,bis-(4-hydroxyphenyl)-sulphone, 1,4-bis-hydroxymethylbenzene,1,4-dihydroxy benzene, 2,2-bis-(4-hydroxyphenyl)-propane,1,3-bis-hydroxyalkyl hydantoin, tris-hydroxyalkyl-isocyanurate andtris-hydroxyalkyltriazolidine-3,5-dione.

Further examples of polyols suitable for the preparation of thepolyester polycarboxylic acids include the hydroxyalkyl etherscorresponding to the following general formula: ##STR12## obtained bythe addition of substituted or unsubstituted alkylene oxides, such asethylene oxide, propylene oxide, butylene oxide or styrene oxide, to theabove-mentioned polyols.

In the above general formula, B and a are as defined above; m representsan integer of from 1 to 7; and R²⁵, R²⁶, R²⁷ and R²⁸ independentlyrepresent a hydrogen atom, a C₁ -C₁₀ aliphatic group optionallysubstituted with halogen, a C₄ -C₈ cycloaliphatic group, a C₇ -C₁₇araliphatic group or a C₆ -C₁₆ aromatic group optionally substitutedwith halogen and/or alkyl and/or alkoxy. R²⁵, R²⁶, R²⁷ and R²⁸preferably represent hydrogen, an alkyl group having from 1 to 4 carbonatoms, preferably methyl or ethyl, or a C₆ -C₁₂ aryl group optionallysubstituted with one or more halogen atoms (in particular chlorineand/or bromine) and/or C₁ -C₄ alkyl groups and/or C₁ -C₄ alkoxy groups,but in particular they represent phenyl.

The following are preferred examples of such polyols: diethylene glycol,triethylene glycol, dipropylene glycol, tripropylene glycol, dibutyleneglycol, 1,4-bis/2-hydroxy-ethoxy/-cyclohexane,1,4-bis/2-hydroxy-ethoxymethane/-cyclohexane,1,4-bis/2-hydroxy-ethoxy/-benzene,4,4'-bis/2-hydroxyethoxy/-diphenylmethane, -diphenylpropane-2, diphenylether, -diphenyl sulphone, -diphenyl ketone and -diphenyl cyclohexane.

The carboxylic acids or carboxylic acid derivatives and polyols usedmay, of course, also be polymeric. Thus, for example,bis-benzene-dicarboxylic acid esters corresponding to the followinggeneral formula: ##STR13## and bis-alkane-dicarboxylic acid esterscorresponding to the following general formula:

    HOOC--CH.sub.2).sub.s  COO--R.sup.30).sub.r  OCC--CH.sub.2).sub.t  COOH

may be used.

In the above general formulae, R²⁹ and R³⁰ independently represent an atleast divalent aromatic group having from 6 to 15 carbon atoms, anaraliphatic group having from 7 to 20 carbon atoms, a saturated orunsaturated aliphatic group having from 2 to 20 carbon atoms, or acycloaliphatic group having from 5 to 15 carbon atoms, which may becondensed with aromatic (C₆ -C₁₂), cycloaliphatic (C₄ -C₁₂) orheterocyclic (C₂ -C₁₂) ring systems and connected through ether, keto,ester or sulpho bridges and may be substituted by halogen or by nitro oralkoxy groups having from 1 to 20 carbon atoms; r represents an integerof from 1 to 20; and s and t, which may be the same or different,represent zero or an integer of from 1 to 20.

The following are preferred examples of (R²⁹)_(r) and (R³⁰)_(r) :##STR14##

These polyester polycarboxylic acids may be prepared by known methods,generally by melting the polycarboxylic acids and polyols together andremoving the water, liberated, possibly by application of a vacuum or bypurging with nitrogen. The progress of the reaction may be followed bytitration of the excess carboxyl groups so that the end of the reactionmay easily be determined.

Hydroxyl polyesters prepared by known methods from polycarboxylic acids,anhydrides, acid chlorides and/or alkyl esters and polyols may, ofcourse, also be reacted with polycarboxylic acids and anhydrides toproduce the polyester polycarboxylic acids. Such polyesters, containinghydroxyl groups, may of course, also be reacted with low molecularweight acid polyesters, i.e. polyesters containing carboxyl groups, toproduce the polyester polycarboxylic acids.

Where branched-chain polyester polycarboxylic acids are required, thesemay be prepared by condensing all the components by solvent-freecondensation in the presence of an at least trifunctional alcohol or anat least trifunctional polycarboxylic acid by the methods describedabove to produce a branched-chain polyester.

Alternatively, the at least trifunctional polyol may be reacted with thedicarboxylic acids or derivatives thereof to form a short-chainpolyester containing carboxyl groups or derivatives thereof, whichpolyester is then condensed with further diols and dicarboxylic acids toform the polyester polycarboxylic acids.

An at least trifunctional polycarboxylic acid may, of course, also reactwith diols to form a branched, short-chain polyester containing hydroxylgroups, which may then be further reacted with diols and dicarboxylicacids to produce the polyester polycarboxylic acids used according tothe present invention.

Branched chain polyester polycarboxylic acids may, of course, also beobtained by reacting polycarboxylic acids which are at least partiallytrifunctional with the above-described polyesters containing hydroxylgroups.

Another group of polymers containing carboxyl groups are the carboxylgroup-containing copolymers consisting of copolymerised units of from 2to 25 parts, by weight, of at least one copolymerisableα,β-ethylenically unsaturated carboxylic acid having from 3 to 5 carbonatoms and from 75 to 98 parts, by weight, of at least one furthercopolymerisable monomer. The α,β-ethylenically unsaturated carboxylicacids may be mono- or dicarboxylic acids, or semi-esters of dicarboxylicacids having from 1 to 12 carbon atoms in the alcohol component.

The following are preferred copolymerisable monomers:

(I) Maleic acid diesters and esters of acrylic or methacrylic acid withC₁ -C₁₂ aliphatic, C₅ or C₆ cycloaliphatic or C₇ or C₈ araliphaticmonohydric alcohols; for example, methyl acrylate, ethyl acrylate,n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butylacrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, dodecylacrylate, and the corresponding methacrylic acid esters and maleic aciddiesters; cyclopentyl acrylate, cyclohexyl acrylate or the correspondingmethacrylic acid esters and maleic acid diesters; benzyl acrylate,β-phenyl ethyl acrylate and corresponding methacrylic acid esters andmaleic acid diesters;

(II) Aromatic vinyl and vinylidene compounds, for example, styrene,α-methyl styrene, α-methyl-p-isopropyl styrene, α-methyl-m-isopropylstyrene, o, an p-chlorostyrene, o- and p-bromostyrene, methyl styrenessubstituted in the nucleus, p-t-butyl styrene and mixtures thereof;

(III) Vinyl ester of organic monocarboxylic acids in which the acidcomponent has from 2 to 4 carbon atoms, such as vinyl acetate and vinylpropionate;

(IV) Mono-olefinically unsaturated halogenated hydrocarbons, such asvinyl chloride or vinylidene chloride, preferably vinyl chloride;

(V) Acrylonitrile, methacrylonitrile, acrylamide and methacrylamide;

(VI) Vinyl alkyl ethers having from 1 to 4 carbon atoms in the alkylgroup, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl etherand vinyl butyl ether.

Preferred copolymers containing carboxyl groups consist of polymerisedunits of:

(a) from 0 to 60%, by weight, of styrene, α-methyl styrene, o- orp-chlorostyrene, o or p-bromostyrene, p-t-butyl styrene or mixturesthereof, preferably styrene;

(b) from 0 to 98%, by weight, of acrylic acid esters having C₁ -C₈aliphatic alcohol groups or methacrylic acid esters having C₁ -C₈aliphatic alcohol groups, or mixtures thereof; and

(c) from 2 to 25%, by weight, of acrylic acid, methacylic acid,itaconic, maleic and fumaric acid semi-esters having from 1 to 8 carbonatoms in the alcohol component, or mixtures thereof, preferably acrylicacid and/or methacrylic acid;

the sum of the percentage contents of (a) to (c) being 100. Instead of(c), the copolymer may contain from 2 to 25% by weight, of at least oneolefinically unsaturated copolymerisable monomer containing hydroxylgroups, such as hydroxyalkyl esters of acrylic, methacrylic, maleic,fumaric or itaconic acid having from 2 to 4 carbon atoms in the alcoholgroup.

When monomers containing hydroxyl groups are used, the copolymersobtained contain hydroxyl groups and may be converted into copolymerscontaining carboxyl groups by a reaction with carboxylic acidanhydrides, such as succinic acid anhydride.

The term "copolymers" is used here to denote not only copolymers havinga statistical distribution of the polymerised monomers or blockcopolymers, but also graft copolymers in which monomers are grafted on apreviously formed homo- or co-polymer. Statistical copolymers arepreferred.

The carboxyl group-containing copolymers used according to the presentinvention are prepared by known methods, such as solvent-free, solution,dispersion or bead polymerisation, preferably by solution polymerisationor solvent-free polymerisation. Such methods have been described, forexample in "Methoden der Organischen Chemie", (Houben-Weyl), 4thEdition, Volume 14/1, pages 24 to 556, Georg Thieme Verlag, Stuttgart,1961, and in German Offenlegunsschrift Nos. 2,600,318 and 1,965,740.

The quantities of the individual components of the powder lacquer bindermay be widely varied.

When the epoxide resins used are exclusively (i.e. in the absence ofcarboxyl polyesters) of the type of diglycidyl ethers of bisphenol Ahaving a melting point of from 50° to 120° C. and an epoxide equivalentof from 400 to 2000, the conventional catalysts, such as dicyandiamide,benzimidazole or guanidine, may advantageously be replaced by theamidine/isocyanate addition products according to the present invention,using proportions, by weight, of resin to catalyst of from 99:1 to85:15, preferably from 97:3 to 88:12.

When however mixtures of epoxide resins of the type of diglycidyl estersof bisphenol A and carboxyl polyesters are used, the proportions in themixture depend on the acid number of the carboxyl polyester. Thus, forexample, if the acid number is from 30 to 40, the proportion, by weight,of epoxide resin/carboxyl polyester is usually from 60:40 to 80:20,preferably 70:30. If the carboxyl polyester has a higher acid number,e.g. from 40 to 110, the conventional proportion, by weight, of epoxideresin to carboxyl polyester used in practice is from 40:60 to 60:40,preferably ca. 50:50.

When using carboxyl polyesters which are hardened by the admixture oftriglycidyl isocyanurate (TGIC) and/or triglycidyl urazole (TGUZ) and/orglycidyl esters, the resin/hardener ratio also depends on the acidnumber of the carboxyl polyester. Thus, the proportion by weight, ofcarboxyl polyesters having an acid number from 30 to 40 to hardeners,such as TGIC and/or TGUZ and/or glydicyl esters, is from 90:10 to 95:5.Carboxyl polyesters having higher acid numbers, such as from 40 to 100,generally require the addition of a higher proportion of hardener sothat the proportion, by weight, of carboxyl polyesters to hardeners,such as TGIC and/or TGUZ and/or glycidyl esters is from 88:12 to 92:8.

Other possible components of powder lacquers, such as pigments, dyes,fillers, levelling agents, agents to render the lacquers thixotropic,dearating agents, UV stabilisers, oxidation inhibitors and quenchers(radical acceptors, such as N-alkyl-substituted piperidines), mattingagents and substances which improve the surface smoothness, may bevaried within a wide range.

Preparation of powder lacquers is usually carried out as follows: Thechosen binders are first mixed with the amidine/isocyanate additioncompounds according to the present invention and optionally otheradditives and then homogenised solvent-free. This may be carried out insuitable apparatus, such as heated kneaders, but is preferably carriedout by extrusion at a temperature which causes a maximum shearing forceto act on the mixture. The upper limit of temperature should not exceed140° C.

When the extruded mass has been cooled to room temperature and suitablysize reduced, it is ground down to a powder lacquer, the aim being toreduce it to particles having an average size of from 40 to 70 μm,preferably ca. 50 μm, depending on the purpose for which the powder isto be used. Any coarse particles measuring more than 100 μm are removedby screening.

Application of the powder lacquers prepared as described above tosuitable substrates may be carried out by known methods, such aselectrostatic powder spraying, whirl sintering, electrostatic whirlsintering, flame spraying or by the application of an aqueous suspensionusing conventional or electrical methods.

After application of the powder lacquer by one of the methods mentionedabove, the coated workpieces are heated to temperatures of 140° C. orabove to harden the lacquer, the heating time depending to a largeextent on the thermal capacity of the coated workpiece or itstemperature before coating.

The advantage obtainable according to the present invention resides in aconsiderable reduction in the so-called "stoving time" and/or loweringof the stoving temperature.

When the isocyanate-masked amidines according to the present inventionare used as hardener compounds for powder lacquers based on epoxideresins of the type of diglycidyl ethers of bisphenol A, additionaladvantages include the excellent compatibility of the resin componentwith the amidine/isocyanate adducts according to the present invention,which in this case act as hardeners, with the result that a high degreeof gloss is achieved. In addition, the preparation of the powder lacqueris facilitated due to the absence of unwanted preliminary reactionbetween resin and hardener during the extrusion process since splittingof the amidine/isocyanate adducts generally does not occur at the givenresidence time of the mixture in the extruder and at the extrusiontemperature required.

A further advantage compared with the use of known hardeners, such asdicyandiamide, amines or guanidines, is to be seen in the fact thatsignificantly better levelling may be achieved according to the presentinvention. The same advantages of using the amidine/isocyanate adductsdescribed are also obtained analogously when the powder lacquer binderused is not an epoxide resin of the type of diglycidyl ether ofbisphenol A, but a mixture thereof with a suitable carboxyl polyester orif for the purpose of obtaining weather-resistant coatings aconventional carboxyl polyester is used as binder containing, ashardener component, TGIC and/or TGUZ and/or suitable glycidyl esters.The amidine/isocyanate adducts described in both cases act as latentcatalysts. In the latter case there is also the problem of reducing theenergy requirement for stoving by lowering the stoving temperatureand/or reducing the stoving time. The problem could hitherto only besolved by adding catalysts which had a deleterious effect on thelevelling of the coatings and/or reduced the stability of the coatingcompound in storage.

The parts indicated in the following Examples are parts by weight.

EXAMPLES I. Preparation of the amidine corresponding to Formula (A) (A:)##STR15## EXAMPLE 1 Preparation of the amidine corresponding to Formula(A) wherein R represents phenyl

768 g (6 mol) of 2,4-diamino(methyl-cyclohexane)(mixture) of isomers),hereinafter referred to as "PH-tolamine", and 200 ml of water areintroduced with stirring and under nitrogen as protective gas into a4-liter three-necked flask equipped with stirrer, thermometer andClaisen bridge with a 1 l receiver flask. 732 g (6 mol) of benzoic acidare added portion-wise in the course of 30 minutes. The temperaturerises to 80° C. The reaction mixture is then rapidly heated to 250° C.and water and excess PH-tolamine distil off. The reaction is terminatedafter 4 hours at 250° C. The distillate contains 250 g of PH-tolamineand water. The reaction product left behind is distilled at ca. 0.3 mbar(up to 240° C.). 733 g of crude product solidifying to yellowishcrystals and 346 g of residue are obtained. Distillation of the crudeproduct yields the following fractions:

First fraction b.p.₀.3 mbar 80°-160° C.=35 g (ca. 90% PH-tolamine).

Main fraction b.p.₀.3 mbar 160°-195° C.=671 g amidine, white crystalsm.p. 50°-60° C., residue 27 g.

EXAMPLE 2 Preparation of the amidine corresponding to Formula (A)wherein R represents H

736 g (16 mol) of formic acid are added portion-wise over a period of 2hours to 2048 g (16 mol) of PH-tolamine and 400 ml of water analogouslyto Example 1. The temperature rises to 90° C. The reaction mixture isthen rapidly heated to 250° C., and water and excess PH-tolamine distiloff. The reaction is completed after 4 hours' stirring at 250° C. Thedistillate contains 806 g of PH-tolamine and water. The reaction productremaining behind is distilled at ca. 0.3 mbar (up to 200° C.). 806 g ofcrude product (yellow oil, b.p.₀.3 mbar 102°-170° C.) are obtained. Theresidue weighs 480 g. Distillation of the crude product yields thefollowing fractions:

First fraction b.p.₀.3 mbar 35°-107° C.=139 g (90% PH-tolamine)

Main fraction b.p.₀.3 mbar 107°-130° C.=595 g

Yellowish oil which gradually solidifies to a resin having a softeningpoint of from 45°-55° C. Residue 62 g.

EXAMPLE 3 Preparation of the adduct of stearyl isocyanate and theamidine from Example 1

59 g (0.2 mol) of stearyl isocyanate are added portionwise over a periodof 20 minutes to 49 g (0.2 mol based on the equivalent weight) of theamidine of Example 1 with stirring under nitrogen as protective gas atfrom 100° to 120° C. in a 250 ml three-neck flask equipped with stirrer,thermometer, reflux condenser and dropping funnel. An almost colourlessresin having a softening point of ca. 35° C. is obtained.

EXAMPLE 4 Preparation of the adduct of stearyl isocyanate and theamidine from Example 2

73.7 g (0.25 mol) of stearyl isocyanate are added portion-wise in thecourse of 20 minutes to 34.5 g (0.25 mol) of the amidine from Example 2at from 100° to 120° C. in a manner analogous to Example 3. A brownishresin is obtained, which is ground to an almost colourless powder havinga softening point of ca. 35° C.

EXAMPLE 5 Preparation of the adduct of tetramethyl guanidine and6-chlorohexyl isocyanate

80.5 g (0.5 mol) of 6-chlorohexyl isocyanate are added portion-wise overa period of 20 minutes to 57.0 g (0.5 mol) of tetramethyl guanidine withstirring under nitrogen as protective gas at from 105° to 110° C. in a250 ml three-necked flask equipped with stirrer, thermometer, refluxcondenser and dropping funnel. The slightly exothermic reaction iscompleted after a further 30 minutes' stirring at 110° C. A slightlyyellowish resin having a softening point ca. of 35° C. is obtained. Theisocyanate content is 0.5%, by weight.

EXAMPLE 6 Preparation of the adduct of hexamethylene diisocyanate andthe amidine from Example 1

42 g (0.25 mol) of hexamethylene diisocyanate are added portion-wiseover a period of 30 minutes to 122.5 g (0.5 mol) of the amidine fromExample 1 at from 120° to 150° C. in a manner analogous to Example 3.Pale yellow crystals melting at from 79° to 86° C. are obtained.

EXAMPLE 7 Preparation of the adduct of isophorone diisocyanate and theamidine from Example 1

33.3 g (0.15 mol) of isophorone diisocyanate are added portion-wise inthe course of 30 minutes to 76.5 g (0.3 mol) of the amidine from Example1 in a manner analogous to Example 3 at from 120° to 130° C.

Pale yellow crystals melting at from 108° to 113° C. are obtained.

EXAMPLE 8 Preparation of the adduct of hexamethylene diisocyanate andthe amidine from Example 2

50.4 g (0.3 mol) of hexamethylene diisocyanate are added portion-wise inthe course of 30 minutes to 82.8 g (0.6 mol) of the amidine from Example2 in a manner analogous to Example 3 at from 130° to 150° C.

Pale yellow crystals melting at from 85° to 90° C. are obtained.

EXAMPLE 9 Preparation of the adduct of isophorone diisocyanate and theamidine from Example 2

44.4 g (0.2 mol) of isophorone diisocyanate are added portion-wise overa period of 30 minutes at from 130° to 185° C. to 55.2 g (0.4 mol) ofthe amidine from Example 2 in a manner analogous to Example 3.

Pale yellow crystals melting at from 155° to 160° C. are obtained.Isocyanate content 0.2%, by weight.

II. Preparation of the powder lacquers EXAMPLE 10

38.5 parts of a carboxyl polyester having an acid number of 36 preparedfrom terephthalic acid (68.64 parts), isophthalic acid (10.27 parts),neopentyl glycol (22.29 parts), ethylene glycol (13.29 parts), andglycerol (2.29 parts) by solvent-free condensation with elimination ofwater are first mixed dry with 25.6 parts of an epoxide resin of thetype of diglycidyl ether of bisphenol A having an epoxide equivalent of850 and a glass transition temperature of 59° C. (DTA) and with 2.5parts of the catalyst according to the present invention from Example 4,33.0 parts of a white pigment of the type of a highly stable titaniumdioxide rutile and 0.4 parts of a levelling agent (density 0.975 g/cm³ ;viscosity 23.3 Pa.s at 20° C.) based on an acrylate oligomer. Thismixture is dispersed in the molten state at temperatures of from 80° to120° C., using a laboratory extruder of Werner & Pfleiderer, Model ZDSK28. After cooling and preliminary size reduction, the extrudate isground to a powder lacquer having an average particle size of 50 μm,using a 200 AS blowing mill, spiral jet mill of Alpine, Augsburg. Afterremoval of the coarse particles larger than 100 μm by screening, thepowder lacquer which is now ready for use is sprayed on double descaled,degreased test sheets (length 165 mm, width 65 mm, thickness 0.8 mm)using an electrostatic spray device of the type ESB, spray gun Model 50458 at a negative voltage of ca. 60 kV. The sheets are then stoved in astoving oven (Kelvi Plast UL 350/S) for 30 minutes at 140° C. Thecoatings are tested by the conventional methods (see Table I).

The lacquer technical properties were tested in these and the followingexperiments by the methods outlined below:

(1) Gelling time of powder lacquer according to draft DIN 55 990 Part 8;

(2) Cupping values according to DIN 53 156 (Erichsen);

(3) Impact deformation from the back, based on ASTM G-14, using a weightof 1 kg and a ball of 1/2 inch diameter; result given in cm.kg (heightof fall.weight);

(4) Grid section test according to DIN 53 151;

(5) Degree of gloss according to Gardner, DIN 67 530, 60° angle;

(6) Levelling, visual assessment.

Comparison experiment to Example 10

39.5 parts of the carboxyl polyester from Example 10 are mixed with 26.3parts of the epoxide resin from Example 10 and 0.8 parts of the unmaskedcatalyst from Example 2 and with pigment and levelling agent as inExample 10 and made up into a powder lacquer analogously to Example 10.The powder lacquer is applied to test sheets as in Example 10 and thenstoved for 30 minutes at 140° C.

For test results see Table I.

EXAMPLE 11

38.9 parts of the carboxyl polyester from Example 10 are mixed with 25.8parts of the epoxide resin from Example 10, 1.9 parts of the catalystfrom Example 3 and pigment and levelling agent as in Example 10 andworked-up into a powder lacquer by the method described in Example 10.The powder lacquer is applied to test sheets as in Example 10 and thenstoved for 30 minutes at 140° C. The coatings are tested by the methodsdescribed (see Table I).

COMPARISON EXPERIMENT TO EXAMPLE 11

39.5 parts of the carboxyl polyester from Example 10 are mixed with 26.3parts of the epoxide resin from Example 10, 0.8 parts of the unmaskedcatalyst from Example 1 and pigment and levelling agent analogously toExample 10 and worked-up into a powder lacquer which is applied to testsheets as in Example 10 and then stoved for 30 minutes at 140° C. (Fortest results see Table I).

                                      TABLE I                                     __________________________________________________________________________                       Comparison to Comparison to                                             Example 10                                                                          Example 10                                                                            Example 11                                                                          Example 11                                   __________________________________________________________________________    Gelling time at 180° C.                                                             64-65 53-54   60-61 52-53                                        (in sec.)                                                                     Cupping values                                                                        Stoving                                                                            >10   9.8     >10   >10                                          Impact deform-                                                                        condi-                                                                             20    5       30    10                                           ation from the                                                                        tions                                                                 back    30 min/                                                               Grid section                                                                          140° C.                                                                     Gt o/o                                                                              Gt o/o  Gt o/o                                                                              Gt o/o                                       Degree of gloss                                                                            92    86      92    86                                           Levelling    better than                                                                         pronounced                                                                            better than                                                                         pronounced                                                in the com-                                                                         texture in the com-                                                                         texture                                                   parison       parison                                                         Example       Example                                            __________________________________________________________________________

EXAMPLE 12

60.81 parts of a commercial carboxyl polyester having an acid number of31 and a glass transition temperature of 72° C. (DTA) are first mixeddry with 4.58 parts of triglycidyl isocyanurate, 0.81 parts of thecatalyst from Example 4, 33.1 parts of a white pigment of the type of ahighly stable titanium dioxide rutile and 0.7 parts of the commerciallevelling agent from Example 10. This mixture is dispersed as asolvent-free melt at temperatures of from 80° to 120° C., using a doublescrew extruder, screw diameter 43 mm, 80 revs/min. The extrudate isworked-up into a powder lacquer analogously to Example 10. The powderlacquer obtained is sprayed on test sheets analogously to Example 10 andstoved for 10 minutes at 160° C. (for test results see Table II).

COMPARISON EXPERIMENT TO EXAMPLE 12

61.32 parts of the carboxyl polyester from Example 12 are worked-up intoa powder lacquer with 4.62 parts of triglycidyl isocyanurate, 0.26 partsof the catalyst from Example 2 and otherwise the same additives as inExample 12 and sprayed on the test sheets described in Example 10 andsubsequently stoved under the same conditions as in Example 12 (for testresults see Table II).

EXAMPLE 13

60.98 parts of the carboxyl polyester from Example 12, 4.59 parts oftriglycidyl isocyanurate, 0.63 parts of the catalyst from Example 3,33.1 parts of a commercial, highly stable rutile titanium dioxide typepigment and 0.7 parts of a commercial levelling agent are worked-up intoa powder lacquer as in Example 10. The lacquer obtained is sprayed ontest sheets analogously to Example 10 and stoved for 10 minutes at 160°C. (for test results see Table II).

COMPARISON EXPERIMENT TO EXAMPLE 13

61.32 parts of the carboxyl polyester from Example 12 are worked-up with4.62 parts of triglycidyl isocyanurate, 0.26 parts of the catalyst fromExample 1 and otherwise the same additives as in Example 13 to produce apowder lacquer which is sprayed on test sheets and subsequently stovedunder the same conditions as in Example 13 (for test results see TableII).

                                      TABLE II                                    __________________________________________________________________________                          Comparison to Comparison to                                             Example 12                                                                          Example 12                                                                            Example 13                                                                          Example 13                                __________________________________________________________________________    Gelling time at 180° C. (sec)                                                          53-54 66-67   58-59 57-59                                     Cupping Stoving 10    10      10    10                                        values  conditions                                                            Impact deform-                                                                        10 min/160° C.                                                                 50    40      60    90                                        ation from the                                                                back                                                                          Grid section    Gt o/o                                                                              Gt o/o  Gt o/o                                                                              Gt o/o                                    Degree of       84    74      84    67                                        Gloss                                                                         Levelling       better                                                                              pronounced                                                                            better                                                                              pronounced                                                than in                                                                             texture than in                                                                             texture                                                   the com-      the com-                                                        parison       parison                                                         Example       Example                                         __________________________________________________________________________

EXAMPLE 14

60.9 parts of a commercial carboxyl polyester having an acid number of31 and a glass transition temperature of 66° C. (DTA) are worked-up with4.6 parts of triglycidyl isocyanurate, 0.7 parts of the catalyst fromExample 5, 33.1 parts of a commercial, highly stable rutile titaniumdioxide type pigment and 0.7 parts of a commercial levelling agent toproduce a powder lacquer analogously to Example 10. The powder lacquerobtained is sprayed on test sheets as in Example 10 and stoved for 10minutes at 160° C. (for test results see Table III).

COMPARISON EXPERIMENT TO EXAMPLE 14

61.31 parts of the carboxyl polyester from Example 14, 4.63 parts oftriglycidyl isocyanate, 0.26 parts of the commercial product,tetramethyl guanidine, and otherwise the same additives as used inExample 14 are worked-up into a powder lacquer which is sprayed on testsheets and then stoved under the same conditions as in Example 14 (fortest results see Table III).

                  TABLE III                                                       ______________________________________                                                                 Comparison to                                                        Example 14                                                                             Example 14                                           ______________________________________                                        Gelling time at 180° C. (sec)                                                            52-53      47-49                                            Depth of cupping                                                                         Stoving    10         >10                                          Impact deforma-                                                                          conditions 70         50                                           tion from the                                                                            10 min/                                                            back       160° C.                                                     Grid section          Gt o/o     Gt o/o                                       Degree of gloss       85         80                                           Levelling             slight orange                                                                            short grained                                                      peel texture                                                                             texture                                      ______________________________________                                    

EXAMPLE 15

39.2 parts of the carboxyl polyester from Example 10 are mixed with 26.1parts of the epoxide resin from Example 10, 1.3 parts of the catalystfrom Example 8 and pigment and levelling agent as in Example 10 andworked-up into a powder lacquer by the method described in Example 10.The powder lacquer is applied to test sheets as in Example 10 and thenstoved for 30 minutes at 140° C. (for test results see Table IV).

COMPARISON EXPERIMENT TO EXAMPLE 15

39.5 parts of the carboxyl polyester from Example 10 are mixed with 26.3parts of the epoxide resin from Example 10, 0.8 parts of unmaskedcatalyst from Example 2 and pigment and levelling agent as in Example 10and worked-up into a powder lacquer by the method described in Example10. The powder lacquer is applied to test sheets as in Example 10 andstoved for 30 minutes at 140° C. (for test results see Table IV).

EXAMPLE 16

39.4 parts of the carboxyl polyester from Example 10 are mixed with 26.1parts of the epoxide resin from Example 10, 1.1 parts of the catalystfrom Example 6 and pigment and levelling agent as in Example 10 andworked-up into a powder lacquer by the method described in Example 10.The powder lacquer is applied to test sheets as in Example 10 and thenstoved for 30 minutes at 140° C. (for test results see Table IV).

COMPARISON EXPERIMENT TO EXAMPLE 16

39.5 parts of the carboxyl polyester from Example 10 are mixed with 26.3parts of the epoxide resin from Example 10, 0.8 parts of the unmaskedcatalyst from Example 1 and pigment and levelling agent as in Example 10and worked-up into a powder lacquer by the method described in Example10. The powder lacquer is applied to test sheets as in Example 10 andthen stoved for 30 minutes at 140° C. (for test results see Table IV).

                                      TABLE IV                                    __________________________________________________________________________                          Comparison to Comparison to                                             Example 15                                                                          Example 15                                                                            Example 16                                                                          Example 16                                __________________________________________________________________________    Gelling time at 180° C. (sec)                                                          51-53 53-54   59-62 52-53                                     Cupping values                                                                        Stoving con-                                                                          10    9.8     10    >10                                       Impact deform-                                                                        ditions 5     5       30    10                                        ation from the                                                                        30 min/140° C.                                                 back                                                                          Grid section    Gt o/o                                                                              Gt o/o  Gt o/o                                                                              Gt o/o                                    Degree of gloss 89    86      94    88                                        Levelling       better than                                                                         pronounced                                                                            better than                                                                         pronounced                                                in the com-                                                                         texture in the com-                                                                         texture                                                   parison       parison                                                         experiment    experiment                                      __________________________________________________________________________

EXAMPLE 17

60.9 parts of the carboxyl polyester from Example 12, 4.6 parts oftriglycidyl isocyanurate, 0.7 parts of the catalyst from Example 9, 33.1parts of a white pigment of the type of a highly stable titanium dioxiderutile, and 0.7 parts of a commercial levelling agent are worked-up intoa powder lacquer analogously to Example 10. The powder lacquer obtainedis sprayed on test sheets as in Example 10 and stoved for 10 minutes at160° C. (for test results see Table V).

COMPARISON EXPERIMENT TO EXAMPLE 17

61.32 parts of the carboxyl polyester from Example 17, 4.62 parts oftriglycidyl isocyanurate, 0.26 parts of the catalyst from Example 2 andotherwise the same additives as in Example 17 are worked-up into apowder lacquer analogously to Example 17. The powder lacquer is sprayedon the test sheets described in Example 10 and then stoved under thesame conditions as in Example 17 (for test results see Table V).

EXAMPLE 18

60.90 parts of the carboxyl polyester from Example 14 are mixed with 4.6parts of triglycidyl isocyanurate, 0.7 parts of the catalyst fromExample 7, 33.1 parts of a commercial, highly stable rutile titaniumdioxide type of pigment and 0.7 parts of a commercial levelling agentand extruded and worked-up into a powder lacquer analogously to Example10. The powder lacquer obtained is sprayed on test sheets as in Example10 and stoved for 10 minutes at 160° C. (for test results see Table V).

COMPARISON EXPERIMENT TO EXAMPLE 18

61.12 parts of the carboxyl polyester from Example 18 are worked-up intoa powder lacquer with 4.62 parts of the polyepoxide from Example 18,0.46 parts of the catalyst from Example 1 and otherwise the sameadditives as in Example 18. The powder lacquer is sprayed on the testsheets described in Example 10 and then stoved under the same conditionsas in Example 18 (for test results see Table V).

                                      TABLE V                                     __________________________________________________________________________                          Comparison to Comparison to                                             Example 17                                                                          Example 17                                                                            Example 18                                                                          Example 18                                __________________________________________________________________________    Gelling time at 180° C. (sec)                                                          54-55 63-65   76-79 43-45                                     Cupping values                                                                        Stoving 10    10      10    10                                        Impact deform-                                                                        conditions                                                                            130   10      80    70                                        ation from the                                                                        10 min/160° C.                                                 back                                                                          Grid section    Gt o/o                                                                              Gt o/o  Gt o/o                                                                              Gt o/o                                    Degree of gloss 83    78      85    77                                        Levelling       better than                                                                         pronounced                                                                            better than                                                                         pronounced                                                in compari-                                                                         texture in compari-                                                                         texture                                                   son experi-   son experi-                                                     ment          ment                                            __________________________________________________________________________

We claim:
 1. Addition products obtainable from monoisocyanates havingfrom 2 to 20 carbon atoms and tetrahydropyrimidines of the formula##STR16## wherein R¹⁰ to R¹⁶ are each hydrogen, alkyl having from 1 to 6carbon atoms, cycloalkyl having from 5 to 10 carbon atoms, aralkylhaving from 7 to 12 carbon atoms, aryl having from 6 to 15 carbon atoms,and also together two geminal or vicinal substituents R¹⁰ to R¹⁶together with the carbon atom to which they are attached comprise acycloaliphatic ring having 5 to 6 carbon atoms.
 2. Addition productsaccording to claim 1 wherein the tetrahydropyrimidines are selected from2-methyl-tetrahydropyrimidine, 2,4-, 2,5- and2,6-dimethyl-tetrahydropyrimidine, 2-ethyl-tetrahydropyrimidine,2-ethyl-4-methyl-tetrahydropyrimidine, 2-benzyl-tetrahydropyrimidine,2-phenyl-tetrahydropyrimidine, 2-phenyl-4-methyl, -5-methyl- and-6-methyl-tetrahydropyrimidine, 2,4-diaza-3-phenyl-7,9,9- and7,7,9-trimethyl-bicyclo-(4,3,0)-nonene-2, and 2,4-diaza-3-methyl-7,9,9-and 7,7,9-trimethyl-bicyclo(4,3,0)-nonene-2 and mixtures thereof.